In shipbuilding, fire protection plays a substantial role with the lining of walls and covers with insulating elements, mainly in publicly accessible ways and areas, whilst this does not apply with the thermal protection. Since for thermal protection in shipbuilding, usually no regulations exist, the ship-owner can meet those thermal protection measures, which he considers adequate. Due to the small gross weight, for the thermal protection primarily fiber glass is used as heat insulating-material, for example with gross densities scarcely over 20 kg/m3 and an λ-arithmetic procedure of 35 mW/mK according to the heat guidance group WLG 035, pursuant to DIN 18165 in the above ground construction.
In particular for passenger liners, however, world-wide standards are prescribed by the International Maritime Organization (IMO), concerning fire protection. These extend all the way from Fire Resistance Category A15 for cab partitions up to Fire Resistance Category A60 for escape routes, engine room, kitchen and such and similar areas, and the Fire Resistance Category A30 may be planned for other zones of the passenger liner. As also determined in other areas of utilization, the Fire Resistance Category of a fire-protection structure is being determined by the fact that a closed room, exposed to the fire test, is exposed to an accordingly high temperature and the length of time up to reaching a prescribed limit temperature is being measured in a neighboring room, separated from the fire-protection structure. The Fire Resistance Category indicates this period of time as a minimum time in minutes.
It is appropriate to refer as relevant parameter for the determination of the suitable damming materials in shipbuilding, where the insulating material thickness are very different, to refer to the weight per unit area, since this parameter embodies the two substantial measured influence variables, i.e. gross density and thickness.
For such fire-protection structures with the Fire Resistance Category A30 or above, so far mainly rock wool was being used as insulation material, due to its temperature resistance index. Such rock wool is usually produced with nozzle blow molding or with external centrifugation, for example the cascade centrifugation process. Relatively rough fibers are formed in the process, with an average geometric diameter above 4 to 12 μm with relatively short length. Based on the production, also a considerable portion of unfiberized material in the form of coarser fiber components results, being present in the product in the foam of so-called “beads”, with the portion comprising approximately 10% to 30% by weight of the material, but not having an insulation effect and, therefore, principally a fire protecting effect.
Compared to felts, mats or fiber glass plates, the advantage of a fire-protection structure with rock wool is represented by the better fire protection behavior, and therefore this latter construction is being exclusively utilized in cases of higher Fire Resistance Categories. The stone wool material comes either as quilted wire net mat with an bonding agent content of approximately 0.7 weight % (dry related to the fiber mass) with a gross density of approximately 90 kg/m3 or as firm plate with an bonding agent content of approximately 0.5 to 2 weight % and a gross density from 80 to 150 kg/m3. In the case of plates the high bonding agent content, in case of a high gross density, leads to a high absolute admission of bonding agent. Since as bonding agent an organic material is usually used, such as phenol formaldehyde resin, a not insignificant increase of fire load results, which in the fire test can lead to a flame projection on the “cold” side of the fire-protection structure, results, which is a failure criterion. Quilted wire net mats again are not everywhere applicable.
Especially, the use of conventional rock wool is not in consonance with substantial other shipbuilding requirements:
One requirement in shipbuilding is the weight minimization, since each additional weight leads to an increase of the traction resistance and, thus, the fuel consumption. The high gross density of usual rock wool products in each case over 80 kg/m3 leads to an unwanted weight increase, due to the high volume of insulation material for the lining of walls and covers, particularly in passenger liners.
A second requirement is economy of space. Inside the ship hull with predetermined external dimensions, the usable surface decreases with each enlargement of the wall thickness. Due to its relative short and thick fibers, however, conventional rock wool features a comparatively small heat-insulating property vis-à-vis conventional fiber glass, so that a larger wall thickness results, in order to attain an identical heat insulation effect. This heat insulation efficiency is, however, one of the conditions for the fire resistance capacity.
In addition, extremely cramped space conditions prevail in a shipyard for the craftsmen. For this reason each trade may bring only such material aboard the vessel which will effectively used by a team of craftsmen and at the end of the end of the operations of said team, material not used must again be removed from vessel. It should thus be insured that eventually insulation material of the damming technician does not eventually affect excessively the work of electricians. Since it must be avoided, in any case, that close to the end of the team work, there is a lack of material, it is always necessary to work with excess material, which initially has to be transported over closes bars and stairs until the place of operation in the vessel, with material having to be returned at the end of the work of the respective team. In this case, high weight and large volume of materials are extremely negative. In this case, it is especially disadvantageous that a compression of the rock wool material is nearly impossible, since it only features a reduced resilience rate. If the rock wool material would be compressed at a stronger rate in view of economy of space, then the danger would arise that the required thickness for assembly would no longer be attained with the subsequent opening of the package.
An additional problem lies in the multiplicity of the used fire protection and heat insulating materials for the different fire resistance categories, respectively for the heat insulations to be integrated. Thus, for each type of material, the corresponding logistic measure has to be taken, and in the event a given type of material should be lacking, normally it is not possible to continue the work with another type of insulating material. This results in considerable logistic problems, especially when the work is taking place in conditions of reduced time frames.
Another problem with vessels is the over head assembly in areas featuring reduced space. This is especially difficult with heavy materials and in the event of using quilted wire net mats, it is affected due to the fact that said material does not feature rigidity and may be in a pending position from retained points. In addition, “beads” falling down from the material during its assembly, in the form of material not fiberized, could negatively affect the work. Also, as a result of the rock wool surface with relatively short and brittle fibers, the haptic index is unsatisfactory, since during assembly, the material does not always feature a pleasant touch.
An important problem during the operation of a vessel are also vibrations. These are present while the engine is operating. Since vibrations of the most different frequencies are also being transferred to the rock wool material, where they cause oscillations of the relatively thick and heavy fibers, as well as the “beads”, provided in an intermediate position, there is also a trend that the connections, caused by the binding agent, may become lose at the crossing sections of the fibers. Especially in the case of vertical fire protection constructions, this may result in depositions of material, with the consequence that the fire protection effect in the upper portion of the construction may be unduly reduced. In the case of horizontal cover constructions, ruptured fiber material may accumulate jointly with “beads” in the lower area of the insulation, and may, in a certain way, be “discharged”, thus affecting subsequent disassembly in view of the large powder rate, which may require additional protective measures for the work.